Abstract Ground-based magnetometer surveys detect high-positive magnetic anomalies (up to 72 000 nT) which coincide with the location of subeconomic, magnetite-associated platinum-group element (PGE) mineralization within the Boston Creek Flow iron-rich basalt, Archean Abitibi Greenstone Belt, Ontario. The magnetic anomalies confirm the presence of magnetite-enriched zones (up to 20 modal%), and reveal that they are ovoid in shape, up to 10 m in size, and along strike from each other in the central gabbro-diorite layer. Geological and geochemical surveys and mineralogical studies indicate that these zones host smaller zones of disseminated chalcopyrite+pyrite, some of which, in turn, host platinum-group minerals (PGM) and are enriched in PGE and related metals (whole-rock Sigma PGE+Au = up to 1000 ppb, Ag = 1300 ppb, Cu = 0.3%, V = 0.1%, Ni = 0.05%, Ti = 2.5%, and Fe = 25%). The coincidence of the high-positive magnetic anomalies with the location of PGE mineralization, points to ground-based magnetometer surveys as a valuable exploration tool for magnetite-associated PGE ore deposits. The distribution of the residual magnetic field anomalies indicate that such surveys are especially useful in: (1) identifying rock types and mapping their distribution in areas of limited outcrop exposure; (2) locating magnetite-enriched gabbroic rock bodies, even in close proximity to serpentinized olivine cumulate rocks; and (3) delineating the detailed geometry of magnetite-enriched rocks that may carry significant amounts of PGE and PGMs. Exploration strategies should be designed to use ground-based geophysical surveys, in conjunction with geological and geochemical surveys, to locate and delineate the geometry of magnetite-enriched zones within thick, differentiated mafic-ultramafic volcanic flows and plutonic bodies.